1. Field of the invention
Present invention relates to PhotoDynamic Therapy (PDT) and cosmetic treatments in general and, in particular, it relates to use of PDT treatment in cosmetic applications to improve skin conditions for aesthetic purpose.
2. Invention Disclosure Statement
Photodynamic therapy (PDT) is a relatively new treatment modality used in cancer treatment and certain other diseases. PDT's dermatological use has great promise because appropriate photosensitizers or photosensitizer precursors can selectively accumulate in abnormal cells. Exposure to an appropriate wavelength activates the photosensitizer. The activated photosensitizer produces cytotoxic singlet oxygen, in cells that have absorbed the photosensitizer. A variety of cutaneous malignancies and cosmetic problems related to the skin can be treated successfully with PDT.
Skin is the largest organ of the body, accounting for 12% to 16% body weight. Skin is made up of two main layers that cover a third fatty layer. The outer layer is the epidermis, and second layer beneath epidermis is the dermis. Under these two skin layers is a fatty layer of subcutaneous tissue. With age the amount of subcutaneous (under-the-skin) fat is reduced resulting in a looser look to the skin. Skin changes, such as wrinkles and sagging skin, are among the most visible signs of aging. Whitening or graying of the hair is another obvious sign of aging.
The anatomy of a wrinkle begins in the dermis (second major skin layer) where collagen and elastin provide attachment support for the underlying muscles. When collagen, which provides strength, and elastin which provides the resilience for skin, weaken, the surface layer of the skin begins to fall forming a wrinkle. Therefore, healthy collagen and elastin is necessary to provide support, elasticity and firmness to the skin so as to appear smooth and even toned.
A primary cause of wrinkling is sun damage. Fair-skinned people who have prolonged sun exposures usually have skin that is much more wrinkled and weather-beaten than people with dark skin. Aging can be of two types, namely intrinsic aging (genetic factors) and extrinsic aging (external environmental factors).
Dermatologists often use Glogau's classification when describing these aging changes.
Glogau Classification for Skin Aging
1. Glogau soft: minimal wrinkles.
2. Glogau moderated: presence of some wrinkles with motion, such as smile lines.
3. Glogau advanced: persistent wrinkles at rest, skin color changes, ecchimosis and solar keratoses.
4. Glogau severe: many persistent wrinkles, no normal skin.
Fine lines and wrinkles arise because of an irregular thickening of the dermis and a decrease in the amount of water that the epidermis can hold. Sun damage and exposure to environmental toxins, i.e. tobacco smoke, and loss of moisture can cause these skin changes.
Deeper lines or furrows are classified as dynamic or static. Dynamic lines appear while muscles are in movement i.e. the activity of facial muscles. Static lines are unchanged with muscle movement. Eventually dynamic lines become static.
Cosmetic products and procedures are booming industries in our age- and beauty-obsessed culture. Billions of dollars are spent each year on skin care (anti-wrinkle/anti-aging) products that promise to erase wrinkles, lighten age spots or fix another skin malady. Cosmetic surgeries are used to erase wrinkles and to make skin deformities appear younger with toned clear skin.
At present, available treatment for wrinkle reduction and skin rejuvenation includes injectable fillers and botulinum toxin. Both are non-ablative/non-surgical procedures suitable for people with busy lifestyles because of their short recovery time. Fillers are short lived and ineffective. Fillers also cause allergic reaction in many patients.
Different skin peeling (ablative) methods used include chemical, mechanical and photothermal. A chemical peel uses trichloroacetic acid (TCA), other Alpha Hydroxy acids (AHA) and phenol. A mechanical peel, also called transcutaneous blepharoplasty, shaves off the outer layer of skin. In most of these peeling procedures depth of peeling cannot be controlled. Thus the inner skin layer is damaged and exposed to the environment. There is also the possibility of scarring and skin pigmentation.
Photo-thermal peel is an ablative laser skin resurfacing method. A pulsed CO2 laser is used for removing periocular and other types of wrinkles. Pulsed CO2 lasers, used for skin resurfacing, are difficult to apply and can cause valleys and ridges because of inconsistent treatment over a large area with small spot size. Heat diffusion is also difficult to control with pulsed CO2 lasers. Er:YAG lasers have also been used for performing laser skin resurfacing. Er:YAG lasers have a very small penetration depth and thus are not very effective for treating deep wrinkles. Er:YAG skin resurfacing is less painful, less inflammatory and heals quicker, when compared to CO2 lasers. However, Er:YAG is unable to stimulate new collagen growth as effectively as the CO2 laser. Therefore, fine wrinkles are usually not eradicated effectively.
In U.S. Pat. No. 7,198,634, Harth et al. disclose a phototherapeutic method for treating inflammatory skin conditions with combined radiation of infrared radiation and ultraviolet/blue light. The light therapy is used to reduce the inflammation in the skin and increase the blood circulation and faster healing. Here the treatment section for aging generally requires about 5-15 sittings followed by periodic maintenance treatment.
In U.S. Pat. No. 7,066,941, Perricone discloses an apparatus for treating aging or damaged skin by irradiation of affected skin with effective amount of blue and or ultraviolet lights having wavelengths of about 400-500 nm. ‘941’ also discloses application of compositions containing compounds like α-hydroxy acids on skin which reputedly enhance light penetration.
Non-ablative light skin rejuvenation is also immensely popular because of the short healing time. In this method the skin epidermis is, generally, not removed as in the case of ablative laser treatment. One example of non-ablative source is an infrared light source. Non-ablative treatments always require multiple sessions and may take several weeks for optimal results.
Other available treatments include radiofrequency, dermabrasion, micro-dermabrasion and topical treatments to restore skin. The topical treatments give the skin a smoother and refreshed appearance.
PhotoDynamic Therapy (PDT) is a recent advancement in facial rejuvenation using blue light, red light or intense pulse light. During PDT, a photosensitizer is applied to the skin; the skin is then exposed to a light source after a determined period of time during which the photosensitizer is absorbed by the cells. Reported side effects include transient burning, stinging, swelling and redness. Side effects are variable depending on the treatment area, length of photosensitizer exposure and the light source used. Post treatment exposure to light can often create further problems and harm skin.
Unfortunately, all known skin rejuvenation suffers from lack of efficacy and/or from risk to the patient. Hence need remains for a new treatment method, which can be used for skin resurfacing in a painless environment with less potential for scarring and with fast recovery to give a younger and smooth looking skin.